In Alzheimer's Disease (AD), the abnormal cleavage of beta amyloid protein precursor from the intracellular membrane often produces a protein Aβ 1-42 which is incompletely removed by normal clearance processes. It has been reported that soluble beta amyloid oligomers are highly neurotoxic. Moreover, over time, this soluble protein assemblage is deposited as a beta amyloid protein Aβ plaque within brain tissue, leading to the local destruction of neurons. The Aβ plaque deposition is also believed to provoke an inflammatory response by microglia and macrophages, which recognize the plaque as a foreign body. These cells are believed to respond to the plaque deposition by releasing pro-inflammatory cytokines and reactive oxygen species (ROS). Although the inflammatory response may be provoked in an effort to clear the brain tissue of the detrimental plaque, it is now believed that this inflammation also injures local neuronal tissue, thereby exacerbating AD. Soluble oligomers of beta amyloid or “ADDLs” are a neurotoxic species implicated in AD pathogenesis. Yang, J. Biol. Chem., 280, 7, Feb. 18, 2005, 5892-5901.
In the book “The Memory Cure” (2003, McGraw-Hill, N.Y., N.Y.), Dr. Majid Fotuhi writes: “Pharmaceutical companies in search of magic drugs to treat Alzheimer's Disease need to pay close attention to curcumin.”
It has been reported that 0.1-1.0 μM curcumin inhibits the in vitro formation of amyloid beta oligomers, and blocks the in vitro toxicity of Aβ1-42 oligomers in differentiated neuroblastoma cells. Yang, J. Biol. Chem., 280, 7, Feb. 18, 2005, 5892-5901. Curcumin also reduced the amount of soluble beta amyloid by 43% when provided in the diet of Alzheimer's Transgenic mice in a low dose of 160 ppm. Lim, J. Neurosci., 2001 Nov. 1, 21(21) 8370-7.
It appears that curcumin also beneficially reduces deposits of beta amyloid. In middle aged female Sprague-Dawley rats, 500 ppm dietary curcumin reduced amyloid beta deposits induced by beta amyloid infusion by about 80%. Frautschy, Neurobiol. Aging, 22, 2001, 993-1005. Curcumin also reduced beta amyloid plaque burden by about 30-40% when provided in the diet of Alzheimer's Transgenic mice in a low dose of 160 ppm. Lim, J. Neurosci., 2001, Nov. 1, 21(21) 8370-7. This is advantageous because it is believed that the oxidative and inflammatory damage caused by AD is linked to microglial response to amyloid beta deposits.
In addition to its beneficial action against soluble beta amyloid, curcumin has considerable anti-oxidative properties and also inhibits the expression of pro-inflammatory cytokines. Frank, Ann. Clin. Psychiatry, 2005 October-Dec. 17, 4, 269-86, and Cole, Neurobiol. Aging, 26S(2005) S133-S136.
Because curcumin is able to effectively act against many targets of AD, it has been hypothesized that the 4.4 fold lower incidence of AD in the Indian population between the ages of 70 and 79 is due to the high dietary consumption of curcumin. Lim, J. Neuroscience, Nov. 1, 2001, 21(21) 8370-77. In those aged 80 years and older, age-adjusted Alzheimer's prevalence in India is roughly one-quarter the rates in the United States (4% versus 15.7%). Frautschy, Neurobiol. Aging, 22, 2001, 993-1005. Curcumin has been identified in review articles as one of the most promising candidates for long term AD study. Frank, Ann. Clin. Psychiatry, 2005 October-Dec. 17, 4, 269-86, and Cole, Neurobiol. Aging, 26S(2005) S133-S136. Curcumin is currently the subject of an FDA approved IND clinical trial at the UCLA Alzheimer Center in the treatment of mild to moderate AD patients. Cole, Neurobiol. Aging, 26S(2005) S133-S136.
Because the above-mentioned in vivo effects of curcumin upon AD symptoms were achieved by providing curcumin in the diet, it appears that curcumin is effectively able to cross the blood brain barrier. As curcumin is highly lipophilic, it is expected to easily cross the blood brain barrier. Frautschy, Neurobiol. Aging, 22, 2001, 993-1005. Indeed, it has been reported that in vivo studies show that curcumin injected peripherally into aged Tg mice crossed the blood brain barrier and bound amyloid plaques. Yang, J. Biol. Chem., 280, 7, Feb. 18, 2005, 5892-5901.